A conventional nail 1 for staplers is shown in FIGS. 1 and 2 and generally includes a shank 11 with a head 10 at a first end of the shank 11 and a tip portion 13 at a second end of the shank 11. A plurality of engaging rings 12 are defined radially in a section of the shank 11. When the nail penetrates through an object 2, the tip portion 13 first penetrates the object 2 and the shank 11 an the engaging rings 12 are merged into the object 2 till the head 1 is completely engaged with the hole made by the penetration. The hole in the object includes an outward curve periphery 20 through which the nail 1 extends. It is noted that the outer diameter of the engaging rings 12 is the same as the diameter of the shank 11 so that the engaging rings 12 cannot firmly engage with the outward curve periphery 20 and the nail 1 can be easily pulled out from the object 2. Another conventional nail 1 is shown in FIGS. 3 and 4, and the engaging rings in FIG. 1 are replaced with longitudinal grooves 120 in the shank 11. Again, the grooves 120 cannot prevent the nail from being pulled out from the object.
The present invention intends to provide a nail that includes flexible and deformable sleeve which is deformed and engaged by the periphery defining the hole in the object so that the nail can be well positioned and cannot be pulled out from the object easily.